In an onsite repair service when some trouble has occurred in an apparatus such as an air conditioner, a service engineer (or service person) needs to visit a place where the apparatus is installed to find and repair the trouble portion. However, similar troubles sometimes occur in different portions of the apparatus. Therefore, if the service engineer has no information on the trouble of the apparatus when conducting an onsite repair service, it may take a lot of time to find where the trouble is. Or he may have to go back and get parts for repair, which he has not brought with him, and visit there again. This could be a great loss of time.
There are some ways of obtaining maintenance information on an apparatus which actually has some trouble. For example, the service engineer for conducting an onsite repair service on the apparatus can presume where the trouble is from his experience, based on the trouble code informed of by the apparatus. Or the service engineer can use the system disclosed in Japanese Patent Laid-open publication No. H06-294668. The system has database of the past trouble cases on the apparatus and provides maintenance information by presuming a new trouble in the apparatus from the similarity between the new one and the past case troubles.